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            <h2 class="toc-title">目录</h2>
            <div class="toc-content" id="toc-content-auto"></div>
        </div><article class="page single"><h1 class="single-title animate__animated animate__flipInX">Java异常处理</h1><div class="post-meta">
            <div class="post-meta-line"><span class="post-author"><a href="/" title="Author" rel="author" class="author"><i class="fas fa-user-circle fa-fw" aria-hidden="true"></i>MC</a></span>&nbsp;<span class="post-category">收录于 <a href="/categories/java/"><i class="far fa-folder fa-fw" aria-hidden="true"></i>Java</a></span></div>
            <div class="post-meta-line"><i class="far fa-calendar-alt fa-fw" aria-hidden="true"></i>&nbsp;<time datetime="2017-07-18">2017-07-18</time>&nbsp;<i class="fas fa-pencil-alt fa-fw" aria-hidden="true"></i>&nbsp;约 1440 字&nbsp;
                <i class="far fa-clock fa-fw" aria-hidden="true"></i>&nbsp;预计阅读 3 分钟&nbsp;<span id="/file%E7%B1%BB/" class="leancloud_visitors" data-flag-title="Java异常处理">
                        <i class="far fa-eye fa-fw" aria-hidden="true"></i>&nbsp;<span class=leancloud-visitors-count></span>&nbsp;次阅读
                    </span>&nbsp;</div>
        </div><div class="details toc" id="toc-static"  data-kept="">
                <div class="details-summary toc-title">
                    <span>目录</span>
                    <span><i class="details-icon fas fa-angle-right" aria-hidden="true"></i></span>
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                <div class="details-content toc-content" id="toc-content-static"><nav id="TableOfContents">
  <ul>
    <li><a href="#1-访问文件和目录">1. 访问文件和目录</a>
      <ul>
        <li><a href="#1-访问与文件名相关的方法">1. 访问与文件名相关的方法</a></li>
        <li><a href="#2-文件检测相关的一些方法">2. 文件检测相关的一些方法</a></li>
        <li><a href="#3-获取文件信息">3. 获取文件信息</a></li>
        <li><a href="#4-文件操作的一些方法">4. 文件操作的一些方法</a></li>
        <li><a href="#5-目录相关的操作">5. 目录相关的操作</a></li>
        <li><a href="#6-测试">6. 测试</a></li>
      </ul>
    </li>
    <li><a href="#2-文件过滤">2. 文件过滤</a></li>
  </ul>
</nav></div>
            </div><div class="content" id="content"><h1 id="file类">File类</h1>
<p><font color = red size = 5>File类的作用是操作文件和目录，但却不能访问文件。</font></p>
<h2 id="1-访问文件和目录">1. 访问文件和目录</h2>
<h3 id="1-访问与文件名相关的方法">1. 访问与文件名相关的方法</h3>
<blockquote>
<p>String getName() 此方法返回File对象所表示的文件名或路径名，如果是路径则返回路径的最后一级子路径名。
String getPath() 返回此File对应的路径名。
File getAbsoluteFile() 返回此File对象的所对应的绝对路径。
String getAbsolutePath() 返回此File对象所对应的绝对路径名。
String getParent() : 返回此File对象所对应目录（最后已经子目录）的父目录名。
boolean renameTo(File newName) : 重命名此File对象所对应的文件或目录，如果重命名成功则返回true；否则返回false。</p>
</blockquote>
<p><font color = green>关于相对路径与绝对路径。</p>
<ol>
<li>绝对路径：绝对路径是一定能访问到的。在windows系统上，如果一个路径是以盘符开头则说明是一个绝对路径。</li>
<li>相对路径：相对于某一文件的路径。</font></li>
</ol>
<p>创建一个File类：</p>
<ol>
<li>FIle (String pathname)
<code>File file1 = new File(&quot;E:\\java&quot;);</code></li>
<li>File (File Parent, String child)
<code>File file2 = new File(file1, &quot;a.txt&quot;);</code></li>
<li>File (String parent, String child)
<code>File file3 = new File(&quot;E:\\java&quot;, &quot;a.txt&quot;)</code></li>
</ol>
<h3 id="2-文件检测相关的一些方法">2. 文件检测相关的一些方法</h3>
<blockquote>
<p>boolean exisit() 判断File文件是否存在
boolean canWrite(): 判断File对象所对应的目录是否可写。
boolean canRead(): 判断File对象所对应的目录是否可读。
boolean isFile() :判断File对象所对应的是否文件。
boolean isDirectory(): 判断File对象所对应的是否目录。
boolean isAbsolute():判断File对象所对应的文件或目录是否是绝对路径。</p>
</blockquote>
<h3 id="3-获取文件信息">3. 获取文件信息</h3>
<blockquote>
<p>long lastModified() : 返回文件最后修改时间。
long length() : 获取文件长度。</p>
</blockquote>
<h3 id="4-文件操作的一些方法">4. 文件操作的一些方法</h3>
<blockquote>
<p>boolean createNewFile() : 当File对象所对应的文件不存在时，该方法将创建一个新的文件，如果创建成功则将返回true，否则将返回false。（有可能File对应的不是文件）
boolean delete() : 删除File所对应的文件。
static File createTempFile(String prefix, String suffix) : 在默认临时文件目录中创建一个空文件，使用给定的前缀、系统生成的随机数和后缀作文文件名。prefix - 用于生成文件名的前缀字符串；必须至少是三字符长，suffix - 用于生成文件名的后缀字符串；可以为 null，在这种情况下，将使用后缀 &ldquo;.tmp&rdquo;。
static File createTempFile(String prefix, String suffix, File directory)：在给定的目录下生成一个文件，文件名前一个方法相同。如果使用默认的目录，第三个参数为null。
void deleteOnExit() : 指定当Java虚拟机退出时，删除File所对应的文件和目录。</p>
</blockquote>
<h3 id="5-目录相关的操作">5. 目录相关的操作</h3>
<blockquote>
<p>boolean mkdir() :  试图创建一个File对象所对应的目录，如果创建成功，则返回true，否则返回false。该方法要求File所对应的是一个路径，而不是文件。
String[] list() : 列出File对象的所有子文件名和路径名。
File listFiles[] ： 列出File所对应的子文件和子路径。
static File[] listRoot() : 列出系统的所有根路径。</p>
</blockquote>
<h3 id="6-测试">6. 测试</h3>
<div class="highlight"><div class="chroma">
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<pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kn">import</span> <span class="nn">java.io.File</span><span class="o">;</span>
</span></span><span class="line"><span class="cl"><span class="kn">import</span> <span class="nn">java.io.IOException</span><span class="o">;</span>
</span></span><span class="line"><span class="cl"><span class="kd">public</span> <span class="kd">class</span> <span class="nc">TestDemo</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">    <span class="kd">public</span> <span class="kd">static</span> <span class="kt">void</span> <span class="nf">main</span><span class="o">(</span><span class="n">String</span><span class="o">[]</span> <span class="n">args</span><span class="o">)</span> <span class="kd">throws</span> <span class="n">IOException</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">        <span class="c1">// 创建File对象
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>        <span class="n">File</span> <span class="n">file1</span> <span class="o">=</span> <span class="k">new</span> <span class="n">File</span><span class="o">(</span><span class="s">&#34;E:\\java\\a&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">File</span> <span class="n">file2</span> <span class="o">=</span> <span class="k">new</span> <span class="n">File</span><span class="o">(</span><span class="s">&#34;b.txt&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">File</span> <span class="n">file3</span> <span class="o">=</span> <span class="k">new</span> <span class="n">File</span><span class="o">(</span><span class="n">file1</span><span class="o">,</span> <span class="s">&#34;c.txt&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="c1">// 访问文件名的相关方法
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>        <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="n">file1</span><span class="o">.</span><span class="na">getName</span><span class="o">());</span>
</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="n">file3</span><span class="o">.</span><span class="na">getParent</span><span class="o">());</span>
</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="n">file1</span><span class="o">.</span><span class="na">getAbsoluteFile</span><span class="o">());</span>
</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="n">file1</span><span class="o">.</span><span class="na">getAbsolutePath</span><span class="o">());</span>
</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="n">file2</span><span class="o">.</span><span class="na">getPath</span><span class="o">());</span>
</span></span><span class="line"><span class="cl">        <span class="c1">// 文件检测的相关方法
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>        <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="n">file2</span><span class="o">.</span><span class="na">exists</span><span class="o">());</span>
</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="n">file2</span><span class="o">.</span><span class="na">canRead</span><span class="o">());</span>
</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="n">file2</span><span class="o">.</span><span class="na">canWrite</span><span class="o">());</span>
</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="n">file1</span><span class="o">.</span><span class="na">isDirectory</span><span class="o">());</span>
</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="n">file1</span><span class="o">.</span><span class="na">isAbsolute</span><span class="o">());</span>
</span></span><span class="line"><span class="cl">        <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="n">file2</span><span class="o">.</span><span class="na">isFile</span><span class="o">());</span>
</span></span><span class="line"><span class="cl">        <span class="c1">// 文件与目录的相关操作
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>        <span class="n">file2</span><span class="o">.</span><span class="na">createNewFile</span><span class="o">();</span>
</span></span><span class="line"><span class="cl">        <span class="n">File</span> <span class="n">file4</span> <span class="o">=</span> <span class="n">File</span><span class="o">.</span><span class="na">createTempFile</span><span class="o">(</span><span class="s">&#34;aaa&#34;</span><span class="o">,</span> <span class="s">&#34;.txt&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">file1</span><span class="o">.</span><span class="na">mkdir</span><span class="o">();</span>
</span></span><span class="line"><span class="cl">        <span class="n">File</span> <span class="n">file5</span> <span class="o">=</span> <span class="n">File</span><span class="o">.</span><span class="na">createTempFile</span><span class="o">(</span><span class="s">&#34;aaa&#34;</span><span class="o">,</span> <span class="s">&#34;.txt&#34;</span><span class="o">,</span> <span class="n">file1</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">file5</span><span class="o">.</span><span class="na">renameTo</span><span class="o">(</span><span class="n">file3</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">String</span><span class="o">[]</span> <span class="n">list</span> <span class="o">=</span> <span class="n">file1</span><span class="o">.</span><span class="na">list</span><span class="o">();</span>
</span></span><span class="line"><span class="cl">        <span class="k">for</span> <span class="o">(</span><span class="n">String</span> <span class="n">str</span> <span class="o">:</span> <span class="n">list</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">            <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="n">str</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="o">}</span>
</span></span><span class="line"><span class="cl">        <span class="n">File</span><span class="o">[]</span> <span class="n">listFile</span> <span class="o">=</span> <span class="n">file1</span><span class="o">.</span><span class="na">listFiles</span><span class="o">();</span>
</span></span><span class="line"><span class="cl">        <span class="k">for</span> <span class="o">(</span><span class="n">File</span> <span class="n">file</span><span class="o">:</span><span class="n">listFile</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">            <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="n">file</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="o">}</span>
</span></span><span class="line"><span class="cl">        <span class="n">File</span><span class="o">[]</span> <span class="n">roots</span> <span class="o">=</span> <span class="n">File</span><span class="o">.</span><span class="na">listRoots</span><span class="o">();</span>
</span></span><span class="line"><span class="cl">        <span class="k">for</span> <span class="o">(</span><span class="n">File</span> <span class="n">root</span> <span class="o">:</span> <span class="n">roots</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">            <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="n">root</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="o">}</span>
</span></span><span class="line"><span class="cl">    <span class="o">}</span>
</span></span><span class="line"><span class="cl"><span class="o">}</span>
</span></span></code></pre></td></tr></table>
</div>
</div><h2 id="2-文件过滤">2. 文件过滤</h2>
<p>File类中的list()方法可以接受一个FilenameFilter参数，通过该参数的可以只列出符合条件的文件。
FilenameFilter接口中包含了一个accept(File dir, String name)的方法，该方法将依次对File的所有子目录或者文件进行迭代，如果该方法返回true，则list()方法会列出该子目录或者文件。</p>
<div class="highlight"><div class="chroma">
<table class="lntable"><tr><td class="lntd">
<pre tabindex="0" class="chroma"><code><span class="lnt"> 1
</span><span class="lnt"> 2
</span><span class="lnt"> 3
</span><span class="lnt"> 4
</span><span class="lnt"> 5
</span><span class="lnt"> 6
</span><span class="lnt"> 7
</span><span class="lnt"> 8
</span><span class="lnt"> 9
</span><span class="lnt">10
</span><span class="lnt">11
</span></code></pre></td>
<td class="lntd">
<pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kd">public</span> <span class="kd">class</span> <span class="nc">FilenameFilterDemo</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">    <span class="kd">public</span> <span class="kd">static</span> <span class="kt">void</span> <span class="nf">main</span><span class="o">(</span><span class="n">String</span><span class="o">[]</span> <span class="n">args</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">        <span class="n">File</span> <span class="n">file</span> <span class="o">=</span> <span class="k">new</span> <span class="n">File</span><span class="o">(</span><span class="s">&#34;E:\\Java\\src\\InputandOutput&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="c1">// 使用Lambda表达式（目标类型为FilenameFilter）实现文件过滤
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>        <span class="n">String</span><span class="o">[]</span> <span class="n">namelist</span> <span class="o">=</span> <span class="n">file</span><span class="o">.</span><span class="na">list</span><span class="o">((</span><span class="n">dir</span><span class="o">,</span> <span class="n">name</span><span class="o">)</span> <span class="o">-&gt;</span> <span class="n">name</span><span class="o">.</span><span class="na">endsWith</span><span class="o">(</span><span class="s">&#34;.java&#34;</span><span class="o">)</span>
</span></span><span class="line"><span class="cl">            <span class="o">||</span> <span class="k">new</span> <span class="n">File</span><span class="o">(</span><span class="n">name</span><span class="o">).</span><span class="na">isDirectory</span><span class="o">());</span>
</span></span><span class="line"><span class="cl">        <span class="k">for</span> <span class="o">(</span><span class="n">String</span> <span class="n">name</span> <span class="o">:</span> <span class="n">namelist</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">            <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="n">name</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="o">}</span>
</span></span><span class="line"><span class="cl">    <span class="o">}</span>
</span></span><span class="line"><span class="cl"><span class="o">}</span>
</span></span></code></pre></td></tr></table>
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